The primary objective of this proposal is to develop a novel ion source for the efficient on-line coupling of a wide array of chromatographic techniques with mass spectrometry. The use of liquid chromatography separation is a prerequisite for high-throughput mass spectrometry analysis of complex proteomics samples. Commonly used electrospray ionization (ESI), although allowing a direct coupling, imposes significant limitations on the mobile phases and additives used in LC separations. The most widely used separation technique, reversed-phase liquid chromatography, is performed in non-optimal conditions to satisfy operational requirements of the electrospray ion source. The proposed ion source will overcome these limitations and provide efficient analyte ionization from a wide range of liquid sample compositions. Thus, the ion source will allow RP-LC to perform in optimal conditions and also the use of chromatographic techniques not previously amenable by direct ESI-MS analysis. PUBLIC HEALTH RELEVANCE: Proteomics studies biological processes by the systematic analysis of proteins expressed in a cell or tissue. It plays an important role in modern life sciences, drug discovery, and clinical applications. We propose a new high-throughput technology for the efficient on- line coupling of a wide array of chromatographic separation techniques with mass spectrometry.